Endocrine Abstracts

Introduction and Objectives: In patients with poorly controlled DM-1, the frequently observed alterations of somatotrophic axis seem to be related to abnormalities in the hypothalamic cholinergic tone regulating this axis. The effects of cholinergic stimulation on GH responses to GHRH were evaluated in patients with poorly controlled DM-1 and the relationship of these responses to metabolic control and kidney function tests.

Subjects and Methods: Microalbuminuria and creatinine clearance (GFR) on 24 h urine samples, and the effects of GHRH plus placebo and plus pyridostigmine on GH and glucose circulating levels were studied in 16 young males: 10 normal controls and 6 patients with poorly controlled DM-1 (HbA1c 9.2%) without retinopathy or nephropathy. On different days, placebo or pyridostigmine (120 mg) were given orally at 0830 and GHRH 50 mcg IV at 0930. Blood samples were drawn at 0830, 0900 and then every 15 min until 1130. Response parameters were calculated. Data are expressed as mean±SEM.

Results: GHRH raised GH levels within each group. However, while GH responses were not different between diabetics and controls after GHRH plus placebo, they were actually higher after GHRH plus pyridostigmine in diabetics (AUC of response of GH: 4085.83±1227.86 vs 1914.46±385.06 ng/ml/120 min, P<0.05). GFR was greater in diabetics, although not significant (134.85±20.62 vs 110.12±8.13 ml/min). GH was not correlated with glucose in any of the tests. Furthermore, HbA1c, microalbuminuria and GFR showed no correlation with GH in diabetics.

Conclusions: In this study, the higher GH responses to GHRH plus pyridostigmine in diabetics suggest that there is an augmented cholinergic tone in poorly controlled DM-1 patients. Furthermore, these findings are not related with the higher GFR observed in diabetics.